The pressure to make money out of it will turn your forum into what could be another subreddit. To repeat HN you'd need to remove pictures (they invoke emotions and attract unsophisticated audience) and all the marketing fluff, hire a team of people who deal with autos on day to day basis (mechanics, salesmen, dealship owners, pro racers, stars like the ex Top Gear team) and advertise everywhere that here's the no bs forum about autos. Wait for 10 years and you'll get a critical mass of audience. You'd still have to pay expensive mods. On top of that you'll have to figure a non-ads business model to support the forum.